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Ch. 18 - Ketones and Aldehydes
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh. 18 - Ketones and AldehydesProblem 47a
Chapter 18, Problem 47a

Show how you would accomplish the following synthetic conversions efficiently and in good yield. You may use any necessary additional reagents and solvents.
(a)

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Step 1: Analyze the starting material and product. The starting material is cyclohexanone, a ketone, and the product is an alkene with an extended chain. This suggests a reaction involving carbon-carbon bond formation and elimination.
Step 2: Identify the type of reaction needed. To convert a ketone to an alkene with an extended chain, a Wittig reaction is a suitable choice. The Wittig reaction involves the use of a phosphonium ylide to replace the carbonyl oxygen with a carbon-carbon double bond.
Step 3: Prepare the phosphonium ylide. React triphenylphosphine with an alkyl halide (e.g., ethyl bromide) to form a phosphonium salt. Then, treat the phosphonium salt with a strong base like sodium hydride (NaH) to generate the ylide.
Step 4: Perform the Wittig reaction. React cyclohexanone with the prepared phosphonium ylide in an appropriate solvent, such as tetrahydrofuran (THF), under controlled conditions. This will result in the formation of the desired alkene.
Step 5: Purify the product. Use techniques such as distillation or chromatography to isolate the alkene product in good yield and purity.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cyclic to Linear Conversion

This concept involves the transformation of cyclic compounds into linear structures, often through ring-opening reactions. Such conversions can be achieved using various reagents that facilitate the cleavage of the cyclic bond, allowing for the formation of a linear chain. Understanding the mechanisms and conditions that favor these reactions is crucial for efficient synthesis.
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Reagents and Solvents

The choice of reagents and solvents is critical in organic synthesis, as they can significantly influence the reaction pathway, yield, and selectivity. For ring-opening reactions, nucleophiles or acids may be used to promote the cleavage of the ring, while solvents can affect solubility and reaction kinetics. Selecting appropriate conditions is essential for optimizing the conversion process.
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Reaction Mechanisms

Understanding the underlying reaction mechanisms is vital for predicting the outcomes of synthetic conversions. Mechanisms describe the step-by-step process of how reactants are transformed into products, including the formation and breaking of bonds. Familiarity with mechanisms helps chemists design efficient synthetic routes and troubleshoot potential issues during reactions.
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Related Practice
Textbook Question

Acetals can serve as protecting groups for 1,2-diols, as well as for aldehydes and ketones. When the acetal is formed from acetone plus the diol, the acetal is called an acetonide. Show the acetonides formed from these diols with acetone under acid catalysis.

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Textbook Question

Acetals can serve as protecting groups for 1,2-diols, as well as for aldehydes and ketones. When the acetal is formed from acetone plus the diol, the acetal is called an acetonide. Show the acetonides formed from these diols with acetone under acid catalysis.

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Textbook Question

Show how you would accomplish the following synthetic conversions efficiently and in good yield. You may use any necessary additional reagents and solvents.

(c)

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Textbook Question

Show how you would accomplish the following synthetic conversions efficiently and in good yield. You may use any necessary additional reagents and solvents.

(b)

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Textbook Question

Show how you would accomplish the following synthetic conversions efficiently and in good yield. You may use any necessary additional reagents and solvents.

(d)

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Textbook Question

The following compounds undergo McLafferty rearrangement in the mass spectrometer. Predict the masses of the resulting charged fragments.

(b) 3-methylhexan-2-one

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